1. Field of the Invention
The present invention relates to a sheet material stacking device for stacking, at a stacking section which is provided at a downstream side, sheet materials which are transported from an upstream side, and to an automatic exposure device for a printing plate by which printing plates which are accommodated in a stacked state are taken one at a time and then ejected after an image has been exposed.
2. Description of the Related Art
A technology has been developed in which, using a printing plate (e.g., a PS (presensitized) plate, a thermal plate, a photopolymer plate, or the like) provided with a recording layer on top of a support, an image is recorded directly on the photopolymer layer of the printing plate by a laser beam or the like (automatic exposure device for a printing plate).
With this sort of technology, images can be recorded on printing plates quickly. Therefore, sequential feeding of the printing plates is required. For this reason, a plurality of the printing plates and interleaf sheets (sheet materials) for protecting surfaces of the printing plates are alternately stored in a magazine in a sequentially stacked state beforehand. In this state, the printing plates and the interleaf sheets are made to standby at predetermined positions, automatically taken one at a time, and fed into an exposure section.
Since the printing plates are photosensitive, they are stored in a darkroom, and there are some cases in which the darkroom is located apart from the place where the automatic exposure device for the printing plate is set. Therefore, a wheeled stand (trolley) for exclusive use is used to convey the printing plates (ordinarily, a plurality of the printing plates are accommodated in a magazine in a stacked state) from the darkroom to the automatic exposure device. The trolley is accommodated at a predetermined position (accommodating section) of the automatic exposure device in a state of having the magazine mounted thereon. After this accommodation, a shutter which is provided at the magazine is opened so that the printing plates can be fed from the darkroom to the automatic exposure device without being exposed to light.
When the printing plates and the interleaf sheets are alternately taken from the magazine which is mounted on the trolley and one of the printing plates is fed into the exposure section, the interleaf sheets which are separated and taken out from the respective surfaces of the printing plates become unnecessary. Accordingly, these interleaf sheets must be stacked at a predetermined interleaf sheet accommodating section. After the interleaf sheets have been separated and taken out from the surfaces of the printing plates, the interleaf sheets are conveyed by a transport belt and dropped into a back space of the magazine which is mounted on the trolley, and structured therein so that they are accommodated.
However, because each of the interleaf sheets is very thin, when an interleaf sheet is dropped, it tends to behave unstably. With such a structure that the interleaf sheets are accommodated by leaving the stacking of the interleaf sheets to a random dropping thereof, there have been drawbacks in that a number of the interleaf sheets lie upon one another irregularly, and are stacked like a heap of garbage which expands largely so that the back space of the magazine readily becomes full of the interleaf sheets. Further, the interleaf sheet which is transported along the transport belt or the like is charged with static electricity during the transport process, thus causing a phenomenon that the interleaf sheet adheres to internal walls of the interleaf sheet accommodating section during the random dropping of the interleaf sheets. This also causes the stacking performance of the interleaf sheets to deteriorate. In other words, in a conventional structure of stacking the interleaf sheets, it has been difficult to efficiently stack a large quantity (a multiple number) of the interleaf sheets in a limited stacking space.
In view of the aforementioned facts, it is an object of the present invention to provide a sheet material stacking device and an automatic exposure device for a printing plate which are able to stack a number of sheet materials such as interleaf sheets stably and effectively.
An aspect of the present invention is a sheet material stacking device for stacking, at a stacking section which is provided at a downstream side, sheet materials which are transported from an upstream side, comprising: a pair of nipping and feeding members which are disposed at a sheet material transport direction upstream side of the stacking section, which receive the sheet materials which are transported from the upstream side, and which forcibly feed the sheet material to the stacking section; and a guiding device which is disposed at the sheet material transport direction upstream side of the nipping and feeding members, and which guides the sheet materials which are transported from the upstream side into a gap between the nipping and feeding members which face each other.
The sheet material which has been transported from the upstream side is fed into the gap between the nipping and feeding members which face each other, as it is being guided by the guiding device. The sheet material fed into the gap is forcibly fed to the stacking section and stacked. Accordingly, even when the sheet material is extremely thin, this sheet material can behave stably as compared to a case in which the sheet materials are dropped at random and stacked, and can be stacked regularly at the stacking section. Further, a number of the sheet materials can be stacked effectively at the stacking section having a limited space.
Preferably, the sheet material is nipped and transported by the nipping and feeding members at a speed which is faster than the speed at which the sheet material is transported from the upstream side. Therefore, the sheet material which is nipped by the nipping and feeding members maintains a so-called stronger pulling tension, and prevents slackening of the sheet material as the sheet material is being nipped by the nipping and feeding members. As a result, the sheet material does not cause so-called jamming, and can be stacked stably.
Preferably, the nipping and feeding members are the nipping and feeding rollers, i.e., a plurality of skewered rollers provided at a rotational shaft. Therefore, because the sheet material is nipped and transported by the skewered rollers, even when the sheet material is extremely thin, the sheet material cannot wrinkle easily so that the sheet material can be nipped, transported, and fed stably.
Preferably, the sheet material stacking device, further comprising wrap-around prevention boards which are provided such that they follow along projections and indentations formed by each of the plurality of the skewered rollers which are provided at the rotational shaft and which prevent the sheet material which has passed through between the skewered rollers from engaging again with the skewered rollers. Accordingly, since the wrap-around prevention boards are disposed such that then follow along projections and indentations formed by the skewered rollers, the sheet material, which has passed through the skewered rollers and which has been stacked at the stacking section, is prevented from once again wrapping around the skewered rollers.
Preferably, the guiding device has anti-static brushes which engage with the sheet material which is guided into the gap and which remove static electricity (electric charge) from the sheet material. Therefore, the anti-static brushes engage the sheet materials which are guided into the gap between the facing nipping and feeding members and remove static electricity therefrom. Accordingly, the respective sheet materials, which pass through the rollers 144 and which are fed to the interleaf sheet accommodating section, do not unnecessarily adhere to internal walls of the interleaf accommodating section, thus not deteriorating stacking efficiency of the sheet materials.
Another aspect of the present invention is an automatic exposure device for a printing plate which comprises: a conveying device which is able to mount and convey a magazine in which a plurality of printing plates, each of which has a photosensitive layer on top of a support, and a plurality of interleaf sheets for protecting plate surfaces of the printing plates are in a state of being stacked alternately in a sequential order; and an accommodating device which is able to accommodate the conveying device of the printing plates, and which ejects the printing plates after an image has been exposed; a take-out device which alternately takes the printing plates and the interleaf sheets from the stacked state thereof one at a time from the magazine; and an interleaf sheet stacking device which stacks the interleaf sheets which are transported from the take-out device at an upstream side, at the interleaf sheet accommodating section which is provided at a downstream side, wherein the interleaf stacking device comprises: a pair of nipping and feeding members which are disposed at the interleaf sheet transport direction upstream side of the interleaf sheet accommodating section, which receive the interleaf sheets which are transported from the take-out device, and which forcibly feed the interleaf sheets to the interleaf sheet accommodating section; and a guiding device which is disposed at the interleaf sheet transport direction upstream side of the interleaf sheet accommodating section, and which guides the interleaf sheets which are transported from the take-out device into a gap between the nipping and feeding members.
Therefore, even when the interleaf sheets are extremely thin, as compared to a case of random dropping and stacking of the interleaf sheets, the interleaf sheets can behave stably and can be stacked regularly. Further, a number of interleaf sheets can be stacked effectively at the interleaf sheet accommodating section which has a limited space.